Bcl-2-associated X protein
|It has been suggested that Bax (biochemistry) be merged into this article or section. (Discuss)|
BCL2-associated X protein
|Based on PDB id 1F16|
|RNA expression pattern|
The Bcl-2–associated X protein, or BAX, gene was the first identified pro-apoptotic member of the Bcl-2 protein family. Bcl-2 family members share one or more of the four characteristic domains of homology entitled the Bcl-2 homology (BH) domains (named BH1, BH2, BH3 and BH4), and can form hetero- or homodimers. Bcl-2 proteins act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities.
Bax is a pro-apoptotic Bcl-2 protein containing BH1, BH2 and BH3 domains. In healthy mammalian cells, the majority of Bax is found in the cytosol, but upon initiation of apoptotic signaling, Bax undergoes a conformation shift, and inserts into organelle membranes, primarily the outer mitochondrial membrane. Bax is believed to interact with, and induce the opening of the mitochondrial voltage-dependent anion channel, VDAC. Alternatively, growing evidence suggest that activated Bax and/or Bak form an oligomeric pore, MAC in the outer membrane. This results in the the release of cytochrome c and other pro-apoptotic factors from the mitochondria, often referred to as mitochondrial outer membrane permeabilization, leading to activation of caspases. This defines a direct role for Bax in mitochondrial outer membrane permeabilization, a role common to the Bcl-2 proteins containing the BH1, BH2 and BH3 domains.
The expression of BAX is upregulated by the tumor suppressor protein p53, and Bax has been shown to be involved in p53-mediated apoptosis. The p53 protein is a transcription factor that, when activated as part of the cell's response to stress, regulates many downstream target genes, including BAX. However, p53 also has a transcription-independent role in apoptosis. In particular, p53 interacts with Bax, promoting Bax activation and the insertion of Bax into the mitochondrial membrane.
- BH3 interacting domain death agonist (BID)
- Cytochrome c
- p53 upregulated modulator of apoptosis (PUMA)
- ↑ Oltvai, Z. N.; Milliman, C. L. and Korsmeyer, S. J. (August 1993). "Bcl-2 Heterodimerizes In Vivo with a Conserved Homolog, Bax, That Accelerates Programed Cell Death". Cell 74: 609-619.
- ↑ Wolter, K. G.; Hsu, Y., Smith, C. L., Mechushtan, A., Xi, X., and Youle, R. J. (December 1997). "Movement of Bax from Cytosol to Mitochondria during Apoptosis". Journal of Cell Biology 139: 1281-1292.
- Vieira HL, Haouzi D, El Hamel C, et al. (2001). "Permeabilization of the mitochondrial inner membrane during apoptosis: impact of the adenine nucleotide translocator.". Cell Death Differ. 7 (12): 1146-54. doi:10.1038/sj.cdd.4400778. PMID 11175251.
- Buytaert E, Callewaert G, Vandenheede JR, Agostinis P (2007). "Deficiency in apoptotic effectors Bax and Bak reveals an autophagic cell death pathway initiated by photodamage to the endoplasmic reticulum.". Autophagy 2 (3): 238-40. PMID 16874066.
- Steele AD, Yi CH (2007). "Neuromuscular denervation: Bax up against the wall in amyotrophic lateral sclerosis.". J. Neurosci. 26 (50): 12849-51. PMID 17171827.
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